Field of Invention
This invention relates to carbonating liquids and more particularly to improved means to prepare substantially continuous supplies of carbonated water at low gas and liquid operating pressures.
Post-mix carbonators for commercial applications are described in the literature (see, for example, Lance, U.S. Pat. No. 2,735,665 and Welty et al, U.S. Pat. No. 2,588,677). Such commercial carbonators commonly include a rotary-vane pump with a 1/4 hp. or larger motor, and a welded stainless-steel pressure vessel. The weights of such systems are generally 24 pounds or more. Such post-mix carbonating systems commonly operate with inlet gas pressures of 90 to 110 psi for ambient temperature carbonation. The pump usually supplies liquid to the pressure vessel at pressures generally of the 130 order of pounds per square inch (psi) or greater. Welty, et al, cited above, discloses a gas supply pressure of 80 psi and a liquid supply pressure of 120 to 140 psi, and Lance discloses a gas supply pressure of 100 psi and a liquid supply pressure near 135 psi. Parks in U.S. Pat. No. 4,632,275 discloses liquid supply pressures typically 150-175 pounds in post-mix fountain drink equipment. Commercial equipment embodying the subject matter disclosed in these patents commonly use stainless steel as the material of choice for both the pressure vessel and associated fittings. Such high fluid pressures require costly materials and often preclude the use of inexpensive plastic components.
Another disadvantage of such conventional systems is that the rotary-vane pump is readily destroyed when the input water supply is interrupted while the pump is running. Such a condition can be attributable to an interruption in the municipal water supply for plumbing repairs, or to clogged inlet filters, or the like, and can damage interior pump parts in a short time, resulting in costly repairs and lost beverage sales. While sensors are available to prevent pump damage, these also add incremental cost to the system.
A further disadvantage of conventional systems is the difficulty of separating the pump and the carbonator. Such separation is desirable in applications where safety factors or noise or system centralization is a consideration. System separation is presently accomplished by placing both pump and carbonator in a remote location and by running soda lines to cold plates or other cooling means close to the point of dispensing.
An inherent disadvantage of this arrangement is the tendency of the soda water to decarbonate between the carbonator and the cooling and dispensing location. The situation is exacerbated by routing the connecting soda lines through warm environments. Although decarbonation may be avoided by separating the pump and motor physically from the carbonator the need to install electrical wiring between the two locations makes this option cumbersome and economically undesirable. The need for electrical wiring between the pump and the carbonator also makes it difficult to take advantage, particularly in cold plate installations, of the lower operating pressures possible when the carbonator is supplied with cooled inlet water and immersed in a cooled environment.
Low-pressure carbonators are disclosed in the literature (see, for example, Jacobs et al, U.S. Pat. No. 3,225,965 and Parks, U.S. Pat. No. 3,726,102). These devices operate at or below freezing temperatures and have means to continuously recirculate or otherwise agitate the fluid to be carbonated. While both devices are highly efficient, neither is well suited to post mix or home beverage applications. Further, the low temperatures involved are difficult to achieve in standard post-mix equipment which are in current use.
Another known carbonating apparatus uses carbon dioxide to drive a pump to propel the liquid to be carbonated into a carbonator storage vessel maintained at 25 psi. (See, for example, McMillin, et al, U.S. Pat. No. 4,304,736). Such apparatus is intended to be operated at 0 degrees Celsius, but, both liquid and gas pressures just upstream from the carbonating vessel are near 120 psi.
Still another known low-pressure carbonating apparatus (available from Booth, Inc. of Dallas, Tex.) operates at low gas pressure and liquid pressures. The apparatus includes a dry refrigeration system, a large stainles steel carbonator tank, several syrup tanks, and means for plumbing the unit to a municipal water supply. A disadvantage of this apparatus is inefficient on-line carbonation. Therefore, system performance relies to a substantial degree on carbonation over time by natural absorption and a large reserve supply of soda water carbonated by this process. A further disadvantage of such apparatus is its inability to maintain efficient performance after dispensing several gallons of soda water due to the accumulation of atmospheric gases, as further described hereinafter.
Attempts have been made to introduce carbonators into home refrigerators as post-mix beverage carbonation systems (See, for example, Shikles, Jr. et al, U.S. Pat. No. 2,894,377 and Sedam et al, U.S. Pat. No. Re. 32,179). Difficulties with these systems include relatively large size and high production cost. Such systems include means for storing syrup flavorings and dispensing them simultaneously with carbonated water produced by the system. The syrup storage and dispensing increase both the refrigerator space required and the complexity and cost of the system. With refrigerator shelf space at a premium, the space taken up by such systems reduces flexibility and food storage options available within the refrigerator. The system of Sedam et al represents a considerable advancement in the state of the art but includes several disadvantages. This system relies upon a feed reservoir that must be filled with water as a manual operation requiring some effort and forethought on the part of the user. In addition, there appears to be no easy way to periodically clean the feed reservoir of extraneous materials that may enter during manual filling operations. While the option of using a float valve in the reservoir is discussed, such a valve would introduce tap water into the feed reservoir at tepid temperatures that would reduce carbonator performance. Such temperature increases would also increase dispensing losses as is known in the art. If the user was not sufficiently familiar with the system to add ice to the reservoir, he would perceive variations in levels of carbonation and in beverage quality using a system of this type.
The system described in the aforecited patent to Shikles, Jr. et al also has several other disadvantages. Cool water is held in a small coil wrapped around the carbonator. The coil size appears limitingly small and is in close proximity to the carbonator; hence, heat entering the system from tepid inlet water is easily transferred to the fluid in the carbonator. As a result, the recommended gas operating pressure is approximately 90-100 psi with the further disadvantages that the performance requirements and cost of the entire system are increased. Again, perceivable variations in the level of carbonation can be expected after a very few drinks have been withdrawn from the system. Further, this system requires four supply lines to enter the refrigerator. As an alternative, the supply unit could be placed inside the refrigerator. However, such arrangement takes significantly more storage space and further restricts food storage options for the user. Other considerations include use of a high-pressure pump and other electrical devices inside the refrigerator. Such devices are often costly and further require that electricity be routed to the inside of the refrigerator, an undesirable consideration in retrofit installations.
Additional beverage carbonation devices for operation in the home refrigerator have been described in the literature (see, for example, Berger, U.S. Pat. No. 4,440,318; Catillo U.S. Pat. No. 4,093,681; and Martonoffy U.S. Pat. No. 4,225,537). These devices commonly use a batch-type process for carbonation.
The soda and syrup dispensing apparatus described in the aforecited patent to Berger has some of the same space limiting features described previously. A further space limiting design factor is the carbon dioxide cylinder located in the same housing as the carbonator. Further disadvantages include the relatively cumbersome manual operations required to maintain the system and the waiting period of 5 to 6 hours to carbonate the volume of water. Other disadvantages include the excessive use of carbon dioxide often associated with patch-type systems. Since the gas-storage pressure cylinder is one of the most costly components of a home beverage system, the number of drinks produced by a given amount of carbon dioxide is an important consideration. Excess carbon dioxide usage translates into larger storage cylinders and higher initial costs for a given performance level; or, alternatively, a reduced number of drinks served for a given sized container of carbon dioxide. Since batch-type carbonators such as described in the patent to Berger require venting at the end of each cycle, they generally require more carbon dioxide per drink than carbonators of other designs. The modified batch-type carbonator described in the aforecited patent to Catillo provides an example of high carbon dioxide usage. As disclosed, a volume of carbon dioxide at 90 psig equal to the volume of liquid dispensed is vented during each fill cycle. Thus, the vented carbon dioxide alone is substantially greater than the amount required for good beverage quality. Still another disadvantage encountered in the system disclosed by Catillo is the need for electricity to power the valving system of the device. Additionally, the batch-type carbonator disclosed in the aforecited patent to Martonoffy appears to be more conservative of gas than other batch-type designs, but is believed to supply only low-level carbonation at the end of each cycle and is understood to require frequent manual operations.
Other carbonating apparatus are also disclosed in the literature (See, for example, U.S. Pat. Nos. 4,656,933; 4,655,124; 4,597,509; 4,518,541; 4,475,448; 4,466,342; 4,316,409; 4,242,061; 4,222,825; 4,205,599; 4,173,178; 4,068,010; 3,761,066; 3,756,576; 3,926,102; 3,495,803; 3,408,053 3,397,870; 3,225,965; 2,798,135; 2,735,370; 2,604,310; 2,560,526 1,872,462; 1,115,980; 780,714; and 27,775).